Individual color centers in diamond have recently emerged as a promising solid-state platform for... more Individual color centers in diamond have recently emerged as a promising solid-state platform for quantum communication and quantum information processing systems, as well as sensitive nanoscale magnetometry with optical read-out. Performance of these systems can be significantly improved by engineering optical properties of color centers using nanophotonic approaches. In this work we describe a highflux, room temperature, source of single photons based on an individual Nitrogen-Vacancy (NV) center embedded in a ...
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2003
Electronic absorption spectra of 1,2-diamino-9,10-anthraquinone (12DAAQ), 1,4-diamino-9,10-anthra... more Electronic absorption spectra of 1,2-diamino-9,10-anthraquinone (12DAAQ), 1,4-diamino-9,10-anthraquinone (14DAAQ), 1,5-diamino-9,10-anthraquinone (15DAAQ), and 2,6-diamino-9,10-anthraquinone (26DAAQ) are investigated. Molecular geometries of the amino anthraquinones in the ground state are optimized using the semiempirical ZINDO/1 and AM1 methods without imposing any symmetry constraints. The ground state geometries of all the molecular systems are found to be planar. For interpretation of the spectra, ZINDO/S-CI and AM1-CI calculations employing singly excited configuration using the completely optimized geometry are carried out. Such calculations on the electronic spectra of amino anthraquinones are carried out for the first time. On the basis of these calculations, the assignment of the spectra are successfully made. #
FullereneC 60 thin films on glass substrate (around 2000 thickness) were prepared by thermal evap... more FullereneC 60 thin films on glass substrate (around 2000 thickness) were prepared by thermal evaporation technique. The structural, Surface morphology and optical properties of the film were studied. Optical properties in the spectral range 200 nm to 900 nm of Fullerene C 60 film is investigated by spectrophotometer at different temperature i.e.; room temperature and liquid nitrogen temperature (77K). Optical band gap at room temperature is found to be 2.30 eV, which goes on decreasing and reaches to 2.27 at 77K. Result indicates that C 60 film become more conducting at low temperature. Thickness and refractive index of film was calculated by ellipsometry. From the X ray analysis we have calculated the grain size, dislocation density, number of crystallite per unit area, and strain of the film. The surface morphology of film was analyzed by scanning electron microscope (SEM).
We have studied the optical gain of Fullerene C60 and Fullerene C70 in toluene solution by variab... more We have studied the optical gain of Fullerene C60 and Fullerene C70 in toluene solution by variable strip method. The technique involves the comparison of fluorescence emission at different length of pumped material. The gain is found to be positive for a very narrow range of concentration. The optical gain is maximum at 40 μM concentration for both fullerene molecules. Optical gain is highly concentration dependent and milli molar concentration is not the optimum concentration for the measurement of optical gain. But the value of peak gain for fullerene C70 is more than that of fullerene C60. It may be due to the extent of twisted intermolecular charge transfer (TICT) formation in the excited state is larger for fullerene C70. Therefore, optical gain for fullerene C60 is less than fullerene C70. This is thus an important distinguishing parameter of two sister molecules.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2010
The interaction between Coumarin C440 with Fullerene C 60 has been studied by fluorescence and ti... more The interaction between Coumarin C440 with Fullerene C 60 has been studied by fluorescence and time resolved spectroscopic techniques. The Coumarin C440-Fullerene C 60 pair shows Forster's resonance energy transfer (FRET) from Coumarin C440 (donor) to Fullerenes C 60 (acceptor). The FRET efficiency of this pair increases with the increase of the acceptor concentration. The critical energy transfer distance (R 0 ) at which transfer efficiency is 50% is found to be 34Á. Stern-Volmer plot indicates static as well as dynamic quenching. However, the FRET studies show highest efficiency at the critical stage of dimer formation.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2000
Electronic spectra of phenanthrene (P), 1-methyl phenanthrene (1-MeP), 2-methyl phenanthrene (2-M... more Electronic spectra of phenanthrene (P), 1-methyl phenanthrene (1-MeP), 2-methyl phenanthrene (2-MeP) and their monopositive ions are investigated experimentally as well as theoretically. The ions were produced by photo-oxidation of the hydrocarbons in boric acid matrix. The electronic absorption spectrum of 2-methyl phenanthrene cation (2-MeP + ) is entirely new. For the interpretation of the electronic spectra of neutral and ionized MePs, semi-empirical AM1 (Austin Model 1) calculations are carried out for the first time. The bathochromic shifts in the spectral bands of the neutral and ionized MePs are attributed to 'conjugative' effect. The present experiments reveal that the 448 nm band of 1-methyl phenanthrene cation (1-MeP + ) and the 486 nm band of 2-MeP + show close matching with the respective 450 nm and 488 nm 'diffuse interstellar bands'. This suggests the possibility of the existence of such ionic species in the interstellar matter.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2005
The geometries of hydroxy derivatives of 1,4-naphthoquinone (NQ), viz., 2-hydroxy-1,4-naphthoquin... more The geometries of hydroxy derivatives of 1,4-naphthoquinone (NQ), viz., 2-hydroxy-1,4-naphthoquinone (2HNQ), 5-hydroxy-1,4-naphthoquinone (5HNQ), and 5,8-dihydroxy-1,4-naphthoquinone (DHNQ), have been optimized using the semiempirical and ab initio theoretical methods. Semiempirical methods used for the optimization are Austin Model 1 (AM1) and Zerner's Intermediate Neglect of Differential Overlap/1(ZINDO/1). For ab initio calculations the 6-31G* basis set is used. The electronic spectra of 1,4-naphthoquinone and its hydroxy derivatives are calculated using the semiempirical Zerner's Intermediate Neglect of Differential Overlap/Spectroscopy (ZINDO/S) method employing the geometries optimized at AM1, ZINDO/1 and ab initio levels and compared with their electronic absorption spectra measured by us. For hydroxy substituted systems, such calculations for spectral assignments are made for the first time. It is found that though the predictions of the three theoretical methods for the geometries are similar, the predictions of the ZINDO/S method using the ZINDO/1 optimized geometries, are better for the transition wavelengths in the visible region of the hydroxy substituted naphthoquinones, especially for 5HNQ and DHNQ.
Abstract Cadmium sulphide nanoparticles were synthe-sized by chemical displacement reaction metho... more Abstract Cadmium sulphide nanoparticles were synthe-sized by chemical displacement reaction method using cadmium nitrate as cadmium source and ammonium sul-phide as sulphur source. The CdS samples are character-ized using X-ray diffraction, UVVis ...
Cadmium sulphide nanoparticles were synthesized by chemical displacement reaction method using ca... more Cadmium sulphide nanoparticles were synthesized by chemical displacement reaction method using cadmium nitrate as cadmium source and ammonium sulphide as sulphur source. The CdS samples are characterized using X-ray diffraction, UV–Vis spectroscopy, FTIR spectroscopy, scanning electron microscopy and impedance spectroscopy. CdS nanoparticles are found to possess cubic structure with the crystallite size ~10 nm. The absorption spectra of synthesized CdS nanoparticles revealed the blue shift in excitonic transitions with respect to CdS bulk material, clearly confirming the formation of nanoparticles. The dielectric properties of CdS nanoparticles are studied in the frequency range 103–107 Hz at room temperature. The dielectric properties of CdS nanoparticles are found to be significantly enhanced specially in the low frequency range due to confinement.
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2010
Zinc oxide thin films of different thicknesses ranging from 100 to 300 nm were prepared on polyet... more Zinc oxide thin films of different thicknesses ranging from 100 to 300 nm were prepared on polyethylene terephthalate substrates with thermal evaporation in a vacuum of approximately 3 × 10 −5 Torr. X-ray diffraction patterns confirm the proper phase formation of the material. From atomic force microscopy (AFM) images, it was found that the root mean square roughness of the film surface increased as the film thickness increased. The optical properties of ZnO on PET substrates were determined through the optical transmission method using an ultraviolet-visible spectrophotometer. The optical band gap values of ZnO thin films slightly decreased as the film thickness increased.
Abstract. We have studied the optical gain of Fullerene C60 and Fullerene C70 in toluene solution... more Abstract. We have studied the optical gain of Fullerene C60 and Fullerene C70 in toluene solution by variable strip method. The technique involves the comparison of fluorescence emission at different length of pumped material. The gain is found to be positive for a very ...
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2013
The fluorescence decay time of Fullerenes C60 and C70 in pure form as well as in mixture with Cou... more The fluorescence decay time of Fullerenes C60 and C70 in pure form as well as in mixture with Coumarin C440 and Quinizarine dyes are studied. Results indicate that the decay of pure fullerenes is constant throughout the solute concentration and it is also independent of excitation wavelength, whereas in the case of mixture with dyes different behavior is noticed. We have also calculated the Stern-Volmer quenching constant and optical gain of both the fullerenes from which it is found that the optical gain is positive for Fullerene C70 only in a very narrow range of concentration.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2013
Experimental and theoretical investigation of single-electron capture and additional experimental... more Experimental and theoretical investigation of single-electron capture and additional experimental studies of single-electron loss cross sections in He + -Ar collisions at impact energies of 1.5-5.0 keV for experimental studies and from 10 to 4000 keV for the theoretical calculations are presented. Comparisons are made with other experimental results, for single-electron capture the present measurements confirm the behaviour observed by previous measurements in the energy range 1.5-5.0 keV, except with the data of Eisele and Nagy (1977 J. Chem. Phys. 66 883-5), and for single-electron loss an extrapolation of the high-energy results to low energies shows good agreement with the present data, giving the general shape of the cross section curve. Our theoretical calculations are in good agreement with the experimental data and reproduce the main features of the cross section energy dependence. We present the most important contributions to the total cross sections from the partial capture cross section to the He(1s) and He(n = 2) states, with the former as the dominant channel over the energy region considered.
The amino and hydroxy anthraquinones possess numerous chemically and biologically significant pro... more The amino and hydroxy anthraquinones possess numerous chemically and biologically significant properties and as a group are also of considerable practical importance in the production of dyes & intermediates and as model compounds to gain fundamental information. These derivatives of anthraquinones have found important applications as prominent family of pharmaceutically active and biologically relevant chromophores. A detailed and comprehensive study of electronic absorption spectra of anthraquinone and its hydroxy and amino derivatives and their theoretical interpretation are presented. The effect of solvents on the electronic absorption spectra of anthraquinones is studied using twenty four solvents of different polarities. A careful study of the effect of solvents on the electronic spectra of anthraquinones reveals that the hydrogen bonding effects are of considerable importance in understanding the spectral shifts in the charge transfer transitions. The spectral shifts in various solvents indicate that their values mainly depend on the strength of the hydrogen bonds between the substituent groups and the solvent molecules and the extent of the intramolecular hydrogen bonding.
Individual color centers in diamond have recently emerged as a promising solid-state platform for... more Individual color centers in diamond have recently emerged as a promising solid-state platform for quantum communication and quantum information processing systems, as well as sensitive nanoscale magnetometry with optical read-out. Performance of these systems can be significantly improved by engineering optical properties of color centers using nanophotonic approaches. In this work we describe a highflux, room temperature, source of single photons based on an individual Nitrogen-Vacancy (NV) center embedded in a ...
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2003
Electronic absorption spectra of 1,2-diamino-9,10-anthraquinone (12DAAQ), 1,4-diamino-9,10-anthra... more Electronic absorption spectra of 1,2-diamino-9,10-anthraquinone (12DAAQ), 1,4-diamino-9,10-anthraquinone (14DAAQ), 1,5-diamino-9,10-anthraquinone (15DAAQ), and 2,6-diamino-9,10-anthraquinone (26DAAQ) are investigated. Molecular geometries of the amino anthraquinones in the ground state are optimized using the semiempirical ZINDO/1 and AM1 methods without imposing any symmetry constraints. The ground state geometries of all the molecular systems are found to be planar. For interpretation of the spectra, ZINDO/S-CI and AM1-CI calculations employing singly excited configuration using the completely optimized geometry are carried out. Such calculations on the electronic spectra of amino anthraquinones are carried out for the first time. On the basis of these calculations, the assignment of the spectra are successfully made. #
FullereneC 60 thin films on glass substrate (around 2000 thickness) were prepared by thermal evap... more FullereneC 60 thin films on glass substrate (around 2000 thickness) were prepared by thermal evaporation technique. The structural, Surface morphology and optical properties of the film were studied. Optical properties in the spectral range 200 nm to 900 nm of Fullerene C 60 film is investigated by spectrophotometer at different temperature i.e.; room temperature and liquid nitrogen temperature (77K). Optical band gap at room temperature is found to be 2.30 eV, which goes on decreasing and reaches to 2.27 at 77K. Result indicates that C 60 film become more conducting at low temperature. Thickness and refractive index of film was calculated by ellipsometry. From the X ray analysis we have calculated the grain size, dislocation density, number of crystallite per unit area, and strain of the film. The surface morphology of film was analyzed by scanning electron microscope (SEM).
We have studied the optical gain of Fullerene C60 and Fullerene C70 in toluene solution by variab... more We have studied the optical gain of Fullerene C60 and Fullerene C70 in toluene solution by variable strip method. The technique involves the comparison of fluorescence emission at different length of pumped material. The gain is found to be positive for a very narrow range of concentration. The optical gain is maximum at 40 μM concentration for both fullerene molecules. Optical gain is highly concentration dependent and milli molar concentration is not the optimum concentration for the measurement of optical gain. But the value of peak gain for fullerene C70 is more than that of fullerene C60. It may be due to the extent of twisted intermolecular charge transfer (TICT) formation in the excited state is larger for fullerene C70. Therefore, optical gain for fullerene C60 is less than fullerene C70. This is thus an important distinguishing parameter of two sister molecules.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2010
The interaction between Coumarin C440 with Fullerene C 60 has been studied by fluorescence and ti... more The interaction between Coumarin C440 with Fullerene C 60 has been studied by fluorescence and time resolved spectroscopic techniques. The Coumarin C440-Fullerene C 60 pair shows Forster's resonance energy transfer (FRET) from Coumarin C440 (donor) to Fullerenes C 60 (acceptor). The FRET efficiency of this pair increases with the increase of the acceptor concentration. The critical energy transfer distance (R 0 ) at which transfer efficiency is 50% is found to be 34Á. Stern-Volmer plot indicates static as well as dynamic quenching. However, the FRET studies show highest efficiency at the critical stage of dimer formation.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2000
Electronic spectra of phenanthrene (P), 1-methyl phenanthrene (1-MeP), 2-methyl phenanthrene (2-M... more Electronic spectra of phenanthrene (P), 1-methyl phenanthrene (1-MeP), 2-methyl phenanthrene (2-MeP) and their monopositive ions are investigated experimentally as well as theoretically. The ions were produced by photo-oxidation of the hydrocarbons in boric acid matrix. The electronic absorption spectrum of 2-methyl phenanthrene cation (2-MeP + ) is entirely new. For the interpretation of the electronic spectra of neutral and ionized MePs, semi-empirical AM1 (Austin Model 1) calculations are carried out for the first time. The bathochromic shifts in the spectral bands of the neutral and ionized MePs are attributed to 'conjugative' effect. The present experiments reveal that the 448 nm band of 1-methyl phenanthrene cation (1-MeP + ) and the 486 nm band of 2-MeP + show close matching with the respective 450 nm and 488 nm 'diffuse interstellar bands'. This suggests the possibility of the existence of such ionic species in the interstellar matter.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2005
The geometries of hydroxy derivatives of 1,4-naphthoquinone (NQ), viz., 2-hydroxy-1,4-naphthoquin... more The geometries of hydroxy derivatives of 1,4-naphthoquinone (NQ), viz., 2-hydroxy-1,4-naphthoquinone (2HNQ), 5-hydroxy-1,4-naphthoquinone (5HNQ), and 5,8-dihydroxy-1,4-naphthoquinone (DHNQ), have been optimized using the semiempirical and ab initio theoretical methods. Semiempirical methods used for the optimization are Austin Model 1 (AM1) and Zerner's Intermediate Neglect of Differential Overlap/1(ZINDO/1). For ab initio calculations the 6-31G* basis set is used. The electronic spectra of 1,4-naphthoquinone and its hydroxy derivatives are calculated using the semiempirical Zerner's Intermediate Neglect of Differential Overlap/Spectroscopy (ZINDO/S) method employing the geometries optimized at AM1, ZINDO/1 and ab initio levels and compared with their electronic absorption spectra measured by us. For hydroxy substituted systems, such calculations for spectral assignments are made for the first time. It is found that though the predictions of the three theoretical methods for the geometries are similar, the predictions of the ZINDO/S method using the ZINDO/1 optimized geometries, are better for the transition wavelengths in the visible region of the hydroxy substituted naphthoquinones, especially for 5HNQ and DHNQ.
Abstract Cadmium sulphide nanoparticles were synthe-sized by chemical displacement reaction metho... more Abstract Cadmium sulphide nanoparticles were synthe-sized by chemical displacement reaction method using cadmium nitrate as cadmium source and ammonium sul-phide as sulphur source. The CdS samples are character-ized using X-ray diffraction, UVVis ...
Cadmium sulphide nanoparticles were synthesized by chemical displacement reaction method using ca... more Cadmium sulphide nanoparticles were synthesized by chemical displacement reaction method using cadmium nitrate as cadmium source and ammonium sulphide as sulphur source. The CdS samples are characterized using X-ray diffraction, UV–Vis spectroscopy, FTIR spectroscopy, scanning electron microscopy and impedance spectroscopy. CdS nanoparticles are found to possess cubic structure with the crystallite size ~10 nm. The absorption spectra of synthesized CdS nanoparticles revealed the blue shift in excitonic transitions with respect to CdS bulk material, clearly confirming the formation of nanoparticles. The dielectric properties of CdS nanoparticles are studied in the frequency range 103–107 Hz at room temperature. The dielectric properties of CdS nanoparticles are found to be significantly enhanced specially in the low frequency range due to confinement.
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2010
Zinc oxide thin films of different thicknesses ranging from 100 to 300 nm were prepared on polyet... more Zinc oxide thin films of different thicknesses ranging from 100 to 300 nm were prepared on polyethylene terephthalate substrates with thermal evaporation in a vacuum of approximately 3 × 10 −5 Torr. X-ray diffraction patterns confirm the proper phase formation of the material. From atomic force microscopy (AFM) images, it was found that the root mean square roughness of the film surface increased as the film thickness increased. The optical properties of ZnO on PET substrates were determined through the optical transmission method using an ultraviolet-visible spectrophotometer. The optical band gap values of ZnO thin films slightly decreased as the film thickness increased.
Abstract. We have studied the optical gain of Fullerene C60 and Fullerene C70 in toluene solution... more Abstract. We have studied the optical gain of Fullerene C60 and Fullerene C70 in toluene solution by variable strip method. The technique involves the comparison of fluorescence emission at different length of pumped material. The gain is found to be positive for a very ...
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2013
The fluorescence decay time of Fullerenes C60 and C70 in pure form as well as in mixture with Cou... more The fluorescence decay time of Fullerenes C60 and C70 in pure form as well as in mixture with Coumarin C440 and Quinizarine dyes are studied. Results indicate that the decay of pure fullerenes is constant throughout the solute concentration and it is also independent of excitation wavelength, whereas in the case of mixture with dyes different behavior is noticed. We have also calculated the Stern-Volmer quenching constant and optical gain of both the fullerenes from which it is found that the optical gain is positive for Fullerene C70 only in a very narrow range of concentration.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2013
Experimental and theoretical investigation of single-electron capture and additional experimental... more Experimental and theoretical investigation of single-electron capture and additional experimental studies of single-electron loss cross sections in He + -Ar collisions at impact energies of 1.5-5.0 keV for experimental studies and from 10 to 4000 keV for the theoretical calculations are presented. Comparisons are made with other experimental results, for single-electron capture the present measurements confirm the behaviour observed by previous measurements in the energy range 1.5-5.0 keV, except with the data of Eisele and Nagy (1977 J. Chem. Phys. 66 883-5), and for single-electron loss an extrapolation of the high-energy results to low energies shows good agreement with the present data, giving the general shape of the cross section curve. Our theoretical calculations are in good agreement with the experimental data and reproduce the main features of the cross section energy dependence. We present the most important contributions to the total cross sections from the partial capture cross section to the He(1s) and He(n = 2) states, with the former as the dominant channel over the energy region considered.
The amino and hydroxy anthraquinones possess numerous chemically and biologically significant pro... more The amino and hydroxy anthraquinones possess numerous chemically and biologically significant properties and as a group are also of considerable practical importance in the production of dyes & intermediates and as model compounds to gain fundamental information. These derivatives of anthraquinones have found important applications as prominent family of pharmaceutically active and biologically relevant chromophores. A detailed and comprehensive study of electronic absorption spectra of anthraquinone and its hydroxy and amino derivatives and their theoretical interpretation are presented. The effect of solvents on the electronic absorption spectra of anthraquinones is studied using twenty four solvents of different polarities. A careful study of the effect of solvents on the electronic spectra of anthraquinones reveals that the hydrogen bonding effects are of considerable importance in understanding the spectral shifts in the charge transfer transitions. The spectral shifts in various solvents indicate that their values mainly depend on the strength of the hydrogen bonds between the substituent groups and the solvent molecules and the extent of the intramolecular hydrogen bonding.
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